1. Field of the Invention
The present invention relates to a heat sink with increased cooling capacity, and a semiconductor device comprising the heat sink with increased cooling capacity.
2. Description of the Related Art
In recent years, in addition to the miniaturization and slim structure of semiconductor devices such as LSI, there is a growing demand for increasing the cooling capacity of the heat sink provided in the semiconductor device, in order to meet the increase in the heating quantity of LSI.
In order to effectively dissipate the heat from the heat-producing semiconductor component such as an LSI chip, the heat sink usually includes a base in which a plurality of heat-radiating fins are arranged in parallel formation, and a heat spreader bonded to the surface of the semiconductor component. For example, Japanese Laid-Open Patent Application No. 07-273256 discloses such heat sink. The heat spreader is formed of a thermally conductive metallic material, such as copper. The heat-radiating fins of the base are provided to receive the heat generated by the LSI at the time of operation through the heat spreader and the base, so that the heat received from the LSI is dissipated in the heat-radiating fins. The heat sink provides the increased cooling capacity in this manner, and makes it possible to prevent the temperature of the semiconductor device from exceeding its heat-resistant temperature due to the heat generated at the time of operation.
On the other hand, with the trend of higher integration and higher speed of the semiconductor devices, many LSI chips have the increasing amount of heat generated during operation. In order to increase the cooling capacity of the heat sink more for such semiconductor devices, it is necessary to enlarge the size of the heat sink.
However, the size of the heat sink must meet the restriction requirements in order to develop the composition of the semiconductor device. Hence, it is difficult for the conventional heat sink to meet sufficient cooling capacity by improving only the configuration of the heat sink. For this reason, it is desired to configure the heat sink that allows the miniaturization and slim structure of the semiconductor device wherein the size of the heat sink can be maintained at a level equivalent to the current size without reducing the cooling capacity of the heat sink for a highly heat-producing semiconductor device.
A description will now be given of an example of the embedded-type conventional heat sink using FIG. 1 and FIG. 2.
FIG. 1 shows the composition of the conventional heat sink. FIG. 2 shows the composition of the semiconductor device comprising the conventional heat sink shown in FIG. 1. In FIG. 2, (A) indicates the cross-section of the semiconductor device taken along the one-dot chain line II—II shown in FIG. 1, and (B) indicates the back surface of the semiconductor device shown in FIG. 1.
As shown in FIG. 1 and FIG. 2, the conventional heat sink 1 comprises a base 4 on which a plurality of heat-radiating fins 3 are arranged in parallel formation, and a heat spreader 2 which is bonded to the front surface of the semiconductor device 5.
The semiconductor device 5 is, for example, a heat-producing semiconductor component, such as LSI. The base 4 may be formed of a metallic material, such as aluminium. The heat spreader 2 may be formed of a metallic material, such as copper, which has a heat conductivity higher than that of the metallic material of the base 4.
In the conventional heat sink, by carrying out a predetermined forming process, the heat spreader 2 made of copper is embedded in the back surface of the base 4 made of aluminium, so that the metallic materials are bonded to each other by the metal junction.
As shown in FIG. 2, in the case of the conventional heat sink 1, all the front surface of the heat spreader 2 is brought in contact with the base 4. The front surface of the semiconductor device 5 is bonded to the heat spreader 2 by using the adhesion agent or mechanical junction. Although the semiconductor device 5 generates heat at the time of operation, the heat-radiating fins 3 are provided to receive the heat from the semiconductor device 5 through the heat spreader 2 and the base 4, and the received heat is dissipated in the heat-radiating fins 3.
However, there is the limitation in making small the contact thermal resistance in the interface between the semiconductor device 5 and the heat spreader 2, and the contact thermal resistance in the interface between the heat spreader 2 and the base 4, and in the case of the conventional heat sink, it is difficult to increase the cooling capacity more than a certain level.
Furthermore, in order to efficiently cool the heat-producing semiconductor device, such as LSI, it is necessary to enlarge the thickness of the base and the size (especially height) of the heat sink to some extent. However, the permissible size of the heat sink is restricted according to the composition required for the semiconductor device. Therefore, in the case of the conventional heat sink, it is difficult to increase the cooling capacity for a highly heat-producing semiconductor device while maintaining the size of the heat sink at a level equivalent to the current size.